Useless fact
Why do the F and J keys have small ridges?
The raised ridges on the F and J keys of a keyboard help typists position their index fingers correctly without looking.
The small raised lines or bumps found on the F and J keys of standard computer keyboards are designed to aid touch typists. On a standard QWERTY layout, F and J serve as the resting home position for the left and right index fingers. By feeling these tactile ridges with their fingertips, typists can orient their hands correctly on the home row without having to glance down at the keyboard. This tactile feedback system was patented in 2002 by inventor June E. Botich to enhance typing speed and reduce visual distraction during computer use. A similar tactile guide can also be found on the number five key of a standard numeric keypad, allowing users to locate the center key by feel alone when performing rapid data entry.
Why this is true — International keyboard design standards and patents specify tactile ridges on home row guide keys to enable blind orientation.